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An HTML Application (HTA) is a Microsoft Windows program whose source code consists of HTML, Dynamic HTML, and one or more scripting languages supported by Internet Explorer, such as VBScript or JScript. The HTML is used to generate the user interface, and the scripting language is used for the program logic. An HTA executes without the constraints of the internet browser security model; in fact, it executes as a "fully trusted" application.
The usual file extension of an HTA is
HTAs give the developer the features of HTML together with the advantages of scripting languages. They are popular with Microsoft system administrators who use them for system administration from prototypes to "full-scale" applications, especially where flexibility and speed of development are critical.
Beside the advantage of programming applications in Internet environment programming languages, which can usually be easier, due to the use of markup languages to build a UI (like XAML, which was later presented by Microsoft as a part of WPF), there are a few disadvantages of the current standard of HTA:
An HTA is executed using the program
mshta.exe, or, alternatively, double-clicking on the file. This program is typically installed when Internet Explorer is installed.
mshta.exe executes the HTA by instantiating the Internet Explorer rendering engine (mshtml) as well as any required language engines (such as vbscript.dll).
An HTA is treated like any executable file with extension
.exe. When executed via mshta.exe (or the file icon is double-clicked), it runs immediately. When executed via the browser, the user is asked once, before the HTA is downloaded, whether or not to save or run the application; if saved, it can simply be run on demand after that.
By default, HTAs are rendered as per "standards-mode content in IE7 Standards mode and quirks mode content in IE5 (Quirks) mode", but this can be altered using
When a regular HTML file is executed, the execution is confined to the security model of the web browser, that is, it is confined to communicating with the server, manipulating the page's object model (usually to validate forms and/or create interesting visual effects) and reading or writing cookies.
On the other hand, an HTA runs as a fully trusted application and therefore has more privileges than a normal HTML file; for example, an HTA can create, edit and remove files and registry entries. Although HTAs run in this 'trusted' environment, querying Active Directory can be subject to Internet Explorer Zone logic and associated error messages.
To customize the appearance of an HTA, a new (optional) tag
hta:application was introduced to the
HEAD section. This tag exposes a set of attributes that enable control of border style, the program icon, etc., and provide information such as the argument (commandline) used to launch the HTA.
Otherwise, an HTA has the same format as an HTML page.
An existing HTML file (with file extension
.html, for example) can be changed to an HTA by simply changing the extension to
This is an example of Hello World as an HTML Application.
<HTML> <HEAD> <HTA:APPLICATION ID="HelloExample" BORDER="thick" BORDERSTYLE="complex"/> <TITLE>HTA - Hello World</TITLE> </HEAD> <BODY> <H2>HTA - Hello World</H2> </BODY> </HTML>